The present invention relates to a particular novel class of acrylonitrile-capped polyoxyalkylene compounds and to acrylonitrile-capped polyoxyalkylene-polysiloxane polymers, as well as to the use of said polymers in the formation of cellular urethane products, particularly flexible polyester urethane foam containing a flame-retardant.
It is well known that the urethane linkages of cellular urethanes are formed by the exothermic reaction of a polyfunctional isocyanate and a polyfunctional active hydrogen-containing compound in the presence of a catalyst, and that the cellular structure is provided by gas evolution and expansion during the urethane-forming reaction. Illustrative of suitable active hydrogen-containing compounds are polyether polyols and polyester polyols. In accordance with the "one-shot" process which is the most widely used industrial technique, direct reaction is effected between all of the raw materials which include the polyisocyanate, the active hydrogen-containing compound, the catalyst system, blowing agent and surfactant. A major function of the surfactant is to stabilize the urethane foam, that is, prevent collapse of the foam until the foamed product has developed sufficient gel strength to become self-supporting. Among the various types of silicon-containing compositions reported in the literature as effective stabilizers of urethane foam derived from a polyester polyol and a polyether polyol are e.g. those described in U.S. Pat. No. 3,594,334 and Reissue Pat. No. 27,541, respectively. Other patents relating to the manufacture of flexible polyester urethane foam include U.S. Pat. Nos. 3,563,924; 3,793,360; 3,796,676 and 3,833,512.
In recent years considerable effort has been expended and continues, to reduce the recognized objectionable characteristic of urethane polymers in their ability to ignite readily and burn with an open flame. One approach to this problem is to include a flame-retarding agent such as various phosphorus and/or halogen-containing compounds as a component of the foam-producing reaction mixture, and in this respect, to develop improved and more efficient flame-retarding agents. An associated problem is to provide surfactants which not only function to stabilize foam containing a flame-retardant but which also allow for the formation of such foam which burns at a reduced rate relative to surfactants designed for stabilization of non-flame-retarded foam. For example, certain siloxane surfactants which are excellent stabilizers of non-flame-retarded foam and which are also capable of stabilizing foam containing a flame-retardant appear to have an adverse effect on the efficiency of the flame retarding agent as seen from the flamability properties of some resulting flexible polyester urethane foam products.
It is desirable, therefore, and is an object of this invention to provide a new class of acrylonitrile-capped polyoxyalkylene compounds as well as a new class of acrylonitrile-capped polyoxyalkylene-polysiloxane polymers which polymers, in addition to the ability to stabilize non flame-retarded cellular urethanes, offer particular utility as stabilizers of flexible polyester urethane foam having a flame-retardant incorporated therein.
Various other objects and advantages of this invention will become apparent to those skilled in the art from the accompanying description and disclosure.